package com.itcncp.common.util;

public class Distance {

	private static final double EARTH_RADIUS = 6378137;
	
    private static double rad(double d)
    {
       return d * Math.PI / 180.0;
    }
    
    /**
     * 根据两点间经纬度坐标（double值），计算两点间距离，单位为米
     * @param lng1
     * @param lat1
     * @param lng2
     * @param lat2
     * @return
     */
    public static double computeDistance(double lng1, double lat1, double lng2, double lat2)
    {
       lng1 = lng1 - 0.00001; //纬度相同，经度误差一米，减去
       double radLat1 = rad(lat1);
       double radLat2 = rad(lat2);
       double a = radLat1 - radLat2;
       double b = rad(lng1) - rad(lng2);
       double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a/2),2) +
        Math.cos(radLat1)* Math.cos(radLat2)* Math.pow(Math.sin(b/2),2)));
       s = s * EARTH_RADIUS;
       s = Math.round(s * 10000) / 10000;
       s = s < 0 ? s * -1 : s ;
       return s;
    }
	
}
